Scientists deploy new technique at one of Oregon’s Paisley Caves

A team works inside one of the Paisley Caves in summer 2009

An international team of researchers has reopened a part of the Paisley Caves archaeological site with the aim of resolving a longstanding debate about how and when people first came to the Americas.

Along with UO archaeologist Dennis Jenkins, researchers from three European universities arrived at the caves May 13 to begin a new study funded by the Natural Environment Research Council, a United Kingdom-based funder of environmental science.

Jenkins, a senior archaeologist at the Museum of Natural and Cultural History, is well known for his work at Paisley Caves, located north of Paisley in Oregon's Lake County, where he uncovered long-dried-out feces, or coprolites, that were later identified as being from humans based on the DNA they contained.

The coprolites, radiocarbon dated to as much as 14,300 years ago, distinguish the Paisley Caves as one of the earliest human occupation sites in North America — one that predates by at least 1,000 years the Clovis culture long considered the continent’s oldest cultural tradition. Findings related to the coprolites were detailed in papers published in the journal Science in May 2008 and July 2012.

Still, questions remain, particularly among archaeologists who advocate for the “Clovis First” model for the peopling of the Americas. Scholars in that camp have suggested that the DNA molecules found in the coprolites may not be original to the specimens, but may have migrated from younger sediment layers within in the cave.

That’s where the new study comes in.

Led by Newcastle University archaeologist Lisa-Marie Shillito, the team will use a microscopic technique to analyze organic matter and sediment in the soil of Cave 2 to zero in on the age of the coprolites. By examining the concentration of certain types of lipids — organic matter left by biological organisms — throughout the cave’s sediment layers, Shillito and the team will assess how much movement has occurred over time in the archaeological deposits.

“Based on the site’s stratigraphy, we know there were a lot of people visiting the caves between 12,600 and 12,000 years ago,” Jenkins said. “Did some of their DNA get flushed to deeper sediments via water activity in the cave? Is the DNA as old as the 14,000-year-old layer we found it in? Did the human DNA enter the cave by some other means like animal activity? These are the kinds of questions we’ll be able to answer as a result of this project.”

In addition to the lipid study, the team will take extensive sediment samples for additional analysis.

“Think of it as an archaeological excavation under the microscope,” Shillito said. “Intact blocks of sediments are set in resin and turned into slides for viewing under a microscope. This way we can visually examine the processes by which sediments have been deposited, and whether they have been subsequently altered. We can resolve the fine layers and establish precise sequences of events.”

Shillito and project co-investigator Ian Bull, a chemist at the University of Bristol, have used this new combination of methods in past projects, including at the famous Catalhoyuk site in Turkey.

Shillito, Bull and Jenkins are joined on the project by University of Copenhagen geologist Thomas Stafford, who has been a key figure in developing the evidence for pre-Clovis North American settlement.

“Thanks to years of detailed excavation data on the Paisley Caves’ stratigraphy and archaeology — not to mention an archive of 1,800 coprolites curated by Jenkins at the Museum of Natural and Cultural History — we have a well-documented context for conducting this investigation,” Shillito said.

—by Kristin Strommer, Museum of Natural and Cultural History

NOTE: Limited media access to the site is available through May 23, when the study ends. Media should contact the Museum of Natural and Cultural History at 541-346-5083 to make arrangements. “It’s a unique opportunity to see Cave 2 and its stratigraphy, including the ash layer deposited 7,600 years ago after the eruption of Mount Mazama,” Jenkins said.